Updated: Aug 26
The blood type diet is a fad diet sometimes used in alternative medicine to promote weight loss and fight disease. Alternative medicine typically aims to recognize an individual’s biochemical uniqueness and tailor treatment accordingly. The blood type diet is based on the theory that your blood type determines the foods you should consume in order to achieve optimal health. The diet plan was developed by Peter D'Adamo, a naturopathic physician who theorizes that people respond to various foods depending on their blood type. The blood type diet was introduced in D'Adamo's 1996 book "Eat Right 4 Your Type," which was updated with a 20th Anniversary edition in 2016.
The four different blood types are one marker that can theoretically be used to determine the right diet for your health and vitality. The idea behind the diet is that eating foods with lectins (a type of protein) that are incompatible with a person's blood type can cause blood cell clumping, called agglutination, and result in health problems such as heart or kidney disease or cancer. However, there is a lack of scientific evidence to support these claims.
D'Adamo also believes that a person's blood type affects their ability to digest various foods due to differences in digestive secretions associated with the different blood types. People who are type O, for example, are thought to digest meat well due to high levels of stomach acid. D'Adamo suggests that by following a meal plan designed for your specific blood type, you can digest food with greater efficiency, avoid the negative effects of certain lectins, and—in turn—lose weight and enhance your overall health.
WHAT CAN YOU EAT?
The blood type diet emphasizes certain foods and exercise plans for different blood types. Regardless of blood type, the diet emphasizes eating whole foods and minimizing the intake of processed foods. Here's a closer look at the prescribed plans:
Type A: According to D’Adamo, people with type A blood are predisposed to heart disease, cancer, and diabetes, and do better on an organic, vegetarian diet with calming, centering exercise, such as yoga and tai chi.
Type B: People with type B blood, according to D’Adamo, have a robust immune system and a tolerant digestive system, and are more adaptable than other blood types. He recommends moderate physical exercise and balance exercises, along with a "well-rounded" diet. According to the theory behind the diet, people with type B, however, are more susceptible to autoimmune disorders, such as chronic fatigue, lupus, and multiple sclerosis.
Type AB: People with type AB blood are more biologically complex than other types, according to D’Adamo. Based on this belief, these people supposedly do best with a combination of the exercises and diets for types A and B, though meat should be limited. It is believed that this blood type tends to have lower rates of allergies, but heart disease, cancer, and anemia are common.
Type O: Based on the blood type diet theory, people with type O blood do best with intense physical exercise and animal proteins, while dairy productsand grains may cause problems. According to D’Adamo, gluten, lentils, kidney beans, corn, and cabbage can lead to weight gain in people with this blood type. Health conditions associated with type O include asthma, hay fever, and other allergies, and arthritis.
There is no specific timing for meals or fasting periods required on the blood type diet. However, the plan advises against drinking water or other beverages with meals because it will dilute the natural digestive enzymes and make it more difficult to digest foods.
People with blood type A, who D'Adamo calls the "cultivator," should follow a dairy-free, primarily vegetarian diet with a high intake of fruits, vegetables, grains, beans, legumes, and nuts and seeds.
People with blood type B, who D'Adamo calls "the nomad," should eat a highly varied diet including fruits and vegetables, grains, beans, legumes, meat, poultry, fish, eggs, and dairy, but avoid intake of nuts and seeds.
People with blood type AB, who D'Adamo calls "the enigma," can consume any food recommended for blood types A and B, although aiming for a mainly vegan diet is advised for this type.
People with blood type O, who D'Adamo calls "the hunter," should stick to a dairy-free and grain-free diet high in meat, low in grains, and with a moderate amount of vegetables, eggs, nuts, and seeds.
In addition to specific foods, D'Adamo recommends different supplements for each blood type, which are available on his book's website. There is a specially formulated multivitamin, multimineral, lectin blocker, and probiotic/prebiotic blend for each blood type.
PROS & CONS OF THE BLOOD TYPE DIET
Like all fad diets, the blood type diet has positives and negatives. Here's a closer look at the pros and cons.
The blood type diet encourages exercise. Research shows that regular exercise combined with a healthy diet can lead to weight loss and promote weight management. However, there is no research to support the blood type diet as an effective weight-loss strategy.
Each blood type plan emphasizes choosing whole foods over processed foods, which is a healthy choice.The program also offers a wide variety of compliant foods for some of the blood types, which may make it easier to stick with. Although each blood type comes with its own set of dietary restrictions, the program is not a low-calorie diet with unhealthy restrictions on calorie intake. Plans for types B and AB are more well-rounded and can provide most if not all of the necessary nutrients for a well-balanced diet. However, the plans for types A and O restrict certain healthy food groups, which is not a smart long-term eating plan for many people.
Eating for your specific blood type is not rooted in science. The available research on the blood type diet includes a study published in the journal PLoS One in 2014.5 For the study, 1,455 participants filled out questionnaires designed to determine how frequently they'd consumed certain foods during a one-month period.
In their analysis of the questionnaires, researchers found that following a diet similar to the diet prescribed for blood type A or blood type AB was associated with lower blood pressure and lower cholesterol levels.
Following a diet similar to the diet prescribed for blood type O was associated with lower levels of triglycerides (high levels of this blood fat have been associated with an increased risk of cardiovascular disease), while no significant association was found for the blood type B diet.
Since these associations occurred independently of the participants' blood types, the study's authors concluded that their findings do not back up the overall theory behind the blood type diet.
IS THE BLOOD TYPE DIET HEALTHY FOR YOU?
The blood type diet is based on theory; it isn't rooted in scientific fact and its effectiveness has not been proven in clinical settings. The overall plan does emphasize whole, natural, and unprocessed foods, however, which makes it healthier than some pre-packaged meal plans or meal-replacement plans.
The U.S. Department of Agriculture's 2020–2025 Dietary Guidelines for Americans provide recommendations for a balanced diet. The following nutrient-dense foods are considered part of a healthy diet:
Vegetables of all types and dark, leafy greens (e.g., kale, spinach, broccoli, Swiss chard, green beans)
Fruits, especially whole fruits (e.g., apples, berries, melon)
Grains, especially whole grains (e.g., quinoa, brown rice, oats)
Lean animal protein (e.g., chicken breast, fish, turkey breast, eggs)
Beans and legumes (e.g., beans, lentils, peas)
Nuts and seeds (e.g., walnuts, almonds, sunflower seeds)
Dairy products (e.g., reduced-fat milk, cheese, yogurt, as well as fortified soy-based dairy-free alternatives)
Oils, including oils found in foods (e.g., olive oil, avocado oil, nuts, seafood)
Depending on your blood type, this plan may or may not meet the USDA's definition of a healthy meal plan.
The Type AB diet is the least restrictive and allows for the widest variety of foods to ensure adequate nutrition.
The Type A diet prohibits meat and dairy, which have nutrients, namely protein, that can be found in other foods with careful planning.
The Type B diet also offers a varied diet, with the exception of nuts and seeds, and meets most of the requirements of the USDA healthy eating plan.
The Type O diet avoids dairy and grains, which are considered important parts of a healthy diet, according to the USDA. With careful planning, however, the nutrients found in grains and dairy can be made up by eating a variety of vegetables.
The USDA recommends a reduction of 500 calories per day for weight loss.7 On a 2,000-calorie diet, that's around 1,500 calories per day—but this number varies based on age, sex, weight, and activity level. Use this calculator to determine the right number of calories for you.
The prescribed plans for each blood type in the blood type diet eliminate some foods that are considered crucial to good health. Depending on your blood type, the diet may or may not adhere to federal dietary guidelines and is therefore not a recommended eating plan for overall health or weight management.
Proponents of the blood type diet claim that the program can help you burn fat more efficiently, increase your energy levels, support your immune system, and lower your risk of major health problems like heart disease and cancer. However, there is currently a lack of scientific evidence to support these claims. In addition, there is no research to support that the blood-type diet is an effective weight-loss strategy.
Although proponents of the blood type diet suggest that the use of dietary supplementscan help people following the diet plan meet their nutritional needs, such supplements are not regarded as a reasonable substitute for a healthy, balanced meal plan. Since the diets prescribed for blood types A and O are restrictive, there's some concern that individuals following these diets may fail to achieve sufficient intake of many vitamins and minerals that are essential for health. In addition, a research review published in 2013 found that further studies are still needed to support any of the health claims associated with the blood type diet. In this review, scientists looked at 16 previously published reports on the blood type diet and concluded that "no evidence currently exists to validate the purported health benefits of blood type diets."
While the blood type diet may offer some benefits in certain cases, following a health regimen that combines sensible calorie restriction and regular exercise is generally considered the most effective strategy for weight loss.
Remember, following a long-term or short-term diet may not be necessary for you and many diets out there simply don’t work, especially long-term. While I do not endorse fad diet trends or unsustainable weight loss methods, I present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, budget, and goals. If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.